One of my friends in Camden halls has a car. He had to pay £170 or so for a pass that allowed him to park in the Camden halls' carpark, as well as the CC, as well as parking (and the ticket that he got for parking in the residential part of the street as opposed to the pay and display...).
I know there is a guy in my halls (campbell east) who has his car here, but I don't know how much it costs. I think you can get residence permits for on-street parking, and maybe money off/free congestion charge if your halls are inside the zone.
TBH I wouldn't bother unless you have a specific reason. OH, and insuring cars in London is much more expensive than other parts of the country.